Sinkholes: common, costly and sometimes deadly

By Michael Pearson, CNN

Updated 1031 GMT (1831 HKT) March 4, 2013

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When the ground gives way – An increasing number of sinkholes have appeared in and around the neighborhood where the Lotte World Tower is being built in Seoul, South Korea. The first one was discovered in June and several others have appeared since then, according to local media reports, causing the construction of what would be Seoul's tallest building to come under scrutiny.

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When the ground gives way – Eight Corvettes fell into a sinkhole that opened up beneath a section of the National Corvette Museum in Bowling Green, Kentucky, on February 12. The sinkhole was about 40 feet wide and 25-30 feet deep.

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When the ground gives way – The rear portion of a residential home is consumed by a sinkhole November 14 in Dunedin, Florida.

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When the ground gives way – A 60-foot-wide sinkhole formed underneath the Summer Bay Resort in Clermont, Florida, about 10 minutes from Walt Disney World, on August 11. One resort building collapsed, and another slowly sank.

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When the ground gives way – A backhoe is swallowed by a sinkhole in Montreal, Quebec, Canada, on August 6. The driver of the backhoe was not injured.

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When the ground gives way – A sinkhole killed a guard at a construction site in Shenzhen, China, on March 27. The sinkhole might have been caused by heavy rains and the collapsing of old water pipes running beneath the surface, the Shenzhen Special Zone Daily reported.

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When the ground gives way – Workers watch the demolition of the house where a sinkhole opened three days before in Seffner, Florida, on March 3. Sinkholes caused by acidic groundwater corroding the limestone or carbonate rock underground are common in Florida, according to the Florida Department of Environmental Protection.

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When the ground gives way – Buildings fell into a sinkhole near a subway construction site in Guangzhou, China, in January 2013. The hole measured about 1,000 square feet across and 30 feet deep and was without casualties, according to a state media report.

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When the ground gives way – A basketball court in Ortley Beach, New Jersey, fell into a sinkhole caused by Superstorm Sandy in November 2012.

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When the ground gives way – In July 2011, a man inspects a 40-foot-deep sinkhole that a family found after they heard a booming noise in their kitchen in Guatemala City, Guatemala.

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When the ground gives way – Construction on a subway line caused a huge sinkhole to form in a road in Beijing in April 2011.

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When the ground gives way – An aerial photo shows sinkholes created by the drying of the Dead Sea near Israel in 2011.

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When the ground gives way – A utility worker examines the area around a sinkhole caused by a broken water main in Chevy Chase, Maryland, in December 2010.

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When the ground gives way – Tropical Storm Agatha caused a sinkhole to open in Guatemala City in May 2010.

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When the ground gives way – A fire truck protrudes from a sinkhole as Los Angeles Mayor Antonio Villaraigosa talks to reporters in September 2009.

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When the ground gives way – A water main collapsed an entire block-long part of Ocean Park Boulevard in Santa Monica, California, in December 2002.

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When the ground gives way – In Orlando, a sinkhole 150 feet wide and 60 feet deep swallowed trees, pipelines and a section of sidewalk near an apartment building in June 2002.

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When the ground gives way – A 30-foot-deep sinkhole appeared in a busy street in a suburb east of downtown Los Angeles. A motorist drove into the hole but was rescued before a concrete slab fell onto the car.

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When the ground gives way – "The Great Blue Hole" is the name of a massive underwater sinkhole off the coast of Belize. The deeper you go, the clearer the water becomes, revealing amazing stalactites and limestone.

The kind of sinkhole that suddenly opened up under a Florida home is more common than you might think. Let's take a look at what causes them, where they happen and just how dangerous and costly they can be:

What causes sinkholes?

Many sinkholes form when acidic rainwater dissolves limestone or similar rock beneath the soil, leaving a large void that collapses when it's no longer able to support the weight of what's above, whether that be an open field, a road or a house. These are called "cover-collapse sinkholes," and it would appear this is what's happening in Florida, where the ground beneath the home suddenly gave way.

Where do they happen?

Sinkholes are particularly common in Florida, which rests on a nearly unbroken bed of limestone, according to the Florida Sinkhole Research Institute. Central Florida, including the Tampa area, is particularly known for sinkholes. In fact, Hillsborough County, where Thursday's collapse occurred, is known as part of Florida's so-called Sinkhole Alley, where two-thirds of insurance claims for sinkhole damage occur, according to a report prepared for state lawmakers in 2010. Other places that frequently see sinkholes include Texas, Alabama, Missouri, Kentucky, Tennessee and Pennsylvania, the U.S. Geological Survey says.

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No, some merely cause the ground above to sag, or result in small ponds or saltwater marshes, the Florida Department of Environmental Protection says.

How often do they happen?

There do not appear to be any solid numbers, but the Florida Senate Committee on Banking and Insurance reported that insurers had received 24,671 claims for sinkhole damage in that state alone between 2006 and 2010. That's an average of nearly 17 claims a day, just in Florida.

How dangerous and costly are sinkholes?

Deaths and injuries from sinkholes are rare, but certainly not unheard of. For instance, in 2012, a 15-year-old girl died when her family's car fell into a Utah sinkhole, according to media accounts. But the holes are enormously costly. Insurance claims submitted in Florida alone between 2006 and 2010 totaled $1.4 billion, according the Florida Senate report.